Chapter 15. Managing containers using the Ansible playbook

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   - hosts: managed-node-01.example.com
     vars:
       podman_create_host_directories: true
       podman_firewall:
         - port: 8080-8081/tcp
           state: enabled
         - port: 12340/tcp
           state: enabled
       podman_selinux_ports:
         - ports: 8080-8081
           setype: http_port_t
       podman_kube_specs:
         - state: started
           run_as_user: dbuser
           run_as_group: dbgroup
           kube_file_content:
             apiVersion: v1
             kind: Pod
             metadata:
               name: db
             spec:
               containers:
                 - name: db
                   image: quay.io/db/db:stable
                   ports:
                     - containerPort: 1234
                       hostPort: 12340
                   volumeMounts:
                     - mountPath: /var/lib/db:Z
                       name: db
               volumes:
                 - name: db
                   hostPath:
                     path: /var/lib/db
         - state: started
           run_as_user: webapp
           run_as_group: webapp
           kube_file_src: /path/to/webapp.yml
     roles:
       - linux-system-roles.podma

   This procedure creates a pod with two containers. The podman_kube_specs role variable describes a pod.

   • The run_as_user and run_as_group fields specify that containers are rootless.

   • The kube_file_content field containing a Kubernetes YAML file defines the first container named db. You can generate the Kubernetes YAML file using the podman kube generate command.

     • The db container is based on the quay.io/db/db:stable container image.
     • The db bind mount maps the /var/lib/db directory on the host to the /var/lib/db directory in the container. The Z flag labels the content with a private unshared label, therefore, only the db container can access the content.
   • The kube_file_src field defines the second container. The content of the /path/to/webapp.yml file on the controller node will be copied to the kube_file field on the managed node.
   • Set the podman_create_host_directories: true to create the directory on the host. This instructs the role to check the kube specification for hostPath volumes and create those directories on the host. If you need more control over the ownership and permissions, use podman_host_directories.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check --ask-vault-pass ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook --ask-vault-pass ~/playbook.yml

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   - hosts: managed-node-01.example.com
     vars:
       podman_firewall:
         - port: 8080/tcp
           state: enabled
       podman_kube_specs:
         - state: started
           kube_file_content:
             apiVersion: v1
             kind: Pod
             metadata:
               name: ubi8-httpd
             spec:
               containers:
                 - name: ubi8-httpd
                   image: registry.access.redhat.com/ubi8/httpd-24
                   ports:
                     - containerPort: 8080
                       hostPort: 8080
                   volumeMounts:
                     - mountPath: /var/www/html:Z
                       name: ubi8-html
               volumes:
                 - name: ubi8-html
                   persistentVolumeClaim:
                     claimName: ubi8-html-volume
     roles:
       - linux-system-roles.podman

   The procedure creates a pod with one container. The podman_kube_specs role variable describes a pod.

   • By default, the podman role creates rootful containers.

   • The kube_file_content field containing a Kubernetes YAML file defines the container named ubi8-httpd.

     • The ubi8-httpd container is based on the registry.access.redhat.com/ubi8/httpd-24 container image.

       • The ubi8-html-volume maps the /var/www/html directory on the host to the container. The Z flag labels the content with a private unshared label, therefore, only the ubi8-httpd container can access the content.
       • The pod mounts the existing persistent volume named ubi8-html-volume with the mount path /var/www/html.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml

Procedure

1. Display the contents of the certificate and private key files:

   $ cat ~/certificate.pem
   -----BEGIN CERTIFICATE-----
   ...
   -----END CERTIFICATE-----
   
   $ cat ~/key.pem
   -----BEGIN PRIVATE KEY-----
   ...
   -----END PRIVATE KEY-----

   You require this information in a later step.

2. Store your sensitive variables in an encrypted file:

   1. Create the vault:

      $ ansible-vault create vault.yml
      New Vault password: <vault_password>
      Confirm New Vault password: <vault_password>

   2. After the ansible-vault create command opens an editor, enter the sensitive data in the <key>: <value> format:

      root_password: <root_password>
      certificate: |-
        -----BEGIN CERTIFICATE-----
        ...
        -----END CERTIFICATE-----
      key: |-
        -----BEGIN PRIVATE KEY-----
        ...
        -----END PRIVATE KEY-----

      Ensure that all lines in the certificate and key variables start with two spaces.

   3. Save the changes, and close the editor. Ansible encrypts the data in the vault.

3. Create a playbook file, for example ~/playbook.yml, with the following content:

   - name: Deploy a wordpress CMS with MySQL database
     hosts: managed-node-01.example.com
     vars_files:
       - vault.yml
     tasks:
     - name: Create and run the container
       ansible.builtin.include_role:
         name: rhel-system-roles.podman
       vars:
         podman_create_host_directories: true
         podman_activate_systemd_unit: false
         podman_quadlet_specs:
           - name: quadlet-demo
             type: network
             file_content: |
               [Network]
               Subnet=192.168.30.0/24
               Gateway=192.168.30.1
               Label=app=wordpress
           - file_src: quadlet-demo-mysql.volume
           - template_src: quadlet-demo-mysql.container.j2
           - file_src: envoy-proxy-configmap.yml
           - file_src: quadlet-demo.yml
           - file_src: quadlet-demo.kube
             activate_systemd_unit: true
         podman_firewall:
           - port: 8000/tcp
             state: enabled
           - port: 9000/tcp
             state: enabled
         podman_secrets:
           - name: mysql-root-password-container
             state: present
             skip_existing: true
             data: "{{ root_password }}"
           - name: mysql-root-password-kube
             state: present
             skip_existing: true
             data: |
               apiVersion: v1
               data:
                 password: "{{ root_password | b64encode }}"
               kind: Secret
               metadata:
                 name: mysql-root-password-kube
           - name: envoy-certificates
             state: present
             skip_existing: true
             data: |
               apiVersion: v1
               data:
                 certificate.key: {{ key | b64encode }}
                 certificate.pem: {{ certificate | b64encode }}
               kind: Secret
               metadata:
                 name: envoy-certificates

   The procedure creates a WordPress content management system paired with a MySQL database. The podman_quadlet_specs role variable defines a set of configurations for the Quadlet, which refers to a group of containers or services that work together in a certain way. It includes the following specifications:

   • The Wordpress network is defined by the quadlet-demo network unit.
   • The volume configuration for MySQL container is defined by the file_src: quadlet-demo-mysql.volume field.
   • The template_src: quadlet-demo-mysql.container.j2 field is used to generate a configuration for the MySQL container.
   • Two YAML files follow: file_src: envoy-proxy-configmap.yml and file_src: quadlet-demo.yml. Note that .yml is not a valid Quadlet unit type, therefore these files will just be copied and not processed as a Quadlet specification.
   • The Wordpress and envoy proxy containers and configuration are defined by the file_src: quadlet-demo.kube field. The kube unit refers to the previous YAML files in the [Kube] section as Yaml=quadlet-demo.yml and ConfigMap=envoy-proxy-configmap.yml.

4. Validate the playbook syntax:

   $ ansible-playbook --syntax-check --ask-vault-pass ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

5. Run the playbook:

   $ ansible-playbook --ask-vault-pass ~/playbook.yml